The purpose of this study is to complete the metabolism of sodium and potassium in African-Americans (A-A) and Caucasians (C) and to determine the etiology of any differences since previous studies have demonstrated a diminished natriuresis and kaliuresis in the former group. Initially, approximately six to ten healthy, normotensive A-A and C subjects (both males and females in approximately equal numbers) will be studied. Each subject will be admitted to the GCRC to undergo an intravenous (IV) potassium (K+) tolerance test. Subsequently, each subject will be placed on a fixed diet containing 180 mEq of sodium (Na+) and 100 mEq of K+ per day for 10 to 14 days and remain on this diet as an inpatient in the GCRC. The chloride (Cl) content of the diet will also be fixed. The number of days will be determined when each subject is in balance for these electrolytes. All urine and stool will be collected daily along with periodic blood samples for chemical and hormonal determinations. Initial, height and daily weight and blood pressure will be measured. If A-A subjects demonstrated enhanced cellular K+ uptake on the IV tolerance test, it will be repeated at the end of the balance study in both groups. If, on the other hand, A-A subjects demonstrate increased fecal Na+ and K+ excretion, the dietary study will be repeated while each subject is receiving carbidopa. This drug inhibits the enzyme dopa decarboxylase which is necessary for the production of dopamine, a possible inhibitor of gastrointestinal Na+ and K+ absorption.